Born in Zurich, Glarner spent most of his early years in Naples, where he studied at the Royal Institute of Fine Arts from 1914 to 1920.
After moving to Paris in 1923, he absorbed the influence of Cézanne, Robert Delaunay and other leading modernists as he gradually developed a semi-abstract style. For nine months in 1930-1931 he lived in New York but then returned to Paris. In 1935 he was in Zurich again for a year before heading back to New York, where he soon began to exhibit with the American Abstract artists as he purified his style.
From the mid-1940’s, Glarner focused on Relational Paintings composed of rectangular or nearly rectangular shapes in simple color combinations. Although inspired by the example of Mondrian's Neoplasticism, Glarner's works were less rigid, less doctrinaire, and visually more fluid. As well, he often employed circular formats. In the characteristic Relational Painting, colors were limited to usual red, blue, and yellow, along with black, white, and two shades of grey.
Most of the flat, geometric elements slightly deviated from pure rectangles, suggesting subtle adjustments to composition. Though limited, the composition was intuitively structured, producing a dynamic interaction between discipline and freedom. In 1944, Glarner became a US citizen.
From 1957 he lived in Huntington, on Long Island and by the end of his life returned to Switzerland, where he died, in Locarno.